1. Field of the Invention
This invention relates to ion exchange materials and is particularly concerned with carboxylated cellulose products and their salts having ion exchange properties and with a process for their preparation. The products have particular application in scavenging heavy metal ions from aqueous solution for example in effluent treatment and in precious metal recovery.
2. Description of the Prior Art
Cellulose esters containing free carboxyl groups are well known, in particular the esterification of cellulose with citric acid has been described as a method of textile finishing to improve crease resistance in cellulosic fabrics (Gagliardi and Shippee, American Dyestuff Reporter, Apr. 15, 1963, 74). That such materials exhibited ion exchange properties was noted. U.S. Pat. No. 2,759,787 also describes the preparation of insoluble cellulose citrates by the reaction of citric acid and cellulose. The products are said to be useful as absorbents for high molecular weight materials. Such products have not, however, found general application as ion exchange materials because of their low ion exchange capacity.